Q64 / 160 · TS EAMCET 2020 (09 Sep Shift 1) · Mathematics

Let Z denote the set of integers. Then match the items in list-I, with those of the items in List-II

  List- I   List- II
A sin-1223+sin-113 I kπ±-1kπ6, k∈Z
B sin-1-1n2, n∈Z II kπ±1, k∈Z
C tan-1secπ4+tanπ4 III 32
D sin-1sinx=sin-1sinx⇒x∈ IV 3π8
    V π2

The correct match is

  • A
    ABCDVIIIIII
  • B
    ABCDIVIIVI
  • Correct answer
    C
    ABCDVIIVII
  • D
    ABCDIVIIVIII

Solution

(A) We have sin-1223+sin-113

∵sin-1223=cos-113

∴cos-113+sin-113=π2

(B) Let θ=sin-1-1n2, n∈Z

⇒sinθ=-1n2

⇒sinθ=sin-1nπ6

⇒θ=kπ+-1kπ6, k∈Z

(C) Let α=tan-1secπ4+tanπ4

⇒tanα=secπ4+tanπ4

⇒tanα=2+1

⇒tanα=tan3π8

⇒α=3π8

(D) We have sin-1sinx=sin-1sinx

let sin-1sinx=t

⇒t=t

⇒t=0, 1

Now, sin-1sinx=0 or sin-1sinx=1

Therefore, x=1 or π-1, x∈0,π

Hence, general solution of x=kπ±1, k∈π

Hence, the correct answer is option: 'C'.

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